A motor vehicle electric power steering generally comprises an electromechanical actuator situated on the steering column or on the lower assembly which comprises mechanical components intended to ensure the angular positioning of the steered wheels of the vehicle. The electromechanical actuator comprises a rotary electric motor the shaft of which is supported in at least one rolling bearing, either directly or via a ball screw system. The rolling bearing generally comprises an inner ring, an outer ring, and a row of rolling elements, generally balls, arranged between the rings.
A retaining cage for a rolling bearing comprising a plurality of pockets to house the balls and each of which is defined in part by two claws arranged opposite a heel of the cage is known, from document FR-A1-2 911 934. Such cages are entirely satisfactory in many applications. However, in applications involving a low rotational speed or in applications in which the direction of rotation reverses sharply, this kind of cage runs into various difficulties. Specifically, under the effect of the balls, the cage may suffer extensive deformation and come into contact with the inner ring, causing it to become damaged or even destroyed.
In addition, when the direction in which the load is applied to the rolling bearing changes, as it does for example when the wheels of a vehicle equipped with an electric power steering system as described above are turned as the driver manœuvres to the left and to the right when parking the vehicle, the cage is likewise severely deformed, or even destroyed.
A cage for a rolling bearing comprising first pockets provided with axial retention claws for the axial retention of the cage on the balls, and second pockets with no axial retention claws is also known, from document FR-A1-2 883 941.
In an application involving high axial and radial loads and low rotational speeds, for example speeds of between 100 and 300 rpm, the rolling bearing suffers extensive deformation. Such a cage does not offer the balls enough freedom relative to one another which means that the cage is also severely deformed if two adjacent balls move in opposite directions. This may cause the cage to be destroyed.
The present invention seeks to overcome these disadvantages.